There exist many instances where a liquid in a container is to be dispensed repeatedly in the same, pre-measured quantity. One such situation is the dispensing of a liquid to a user in a medical or assisted living environment, e.g., home care, nursing home, hospital, etc. In the foregoing settings, there have typically been two different methods for dispensing exactly-repeated quantities of a liquid to a user. The first method consists of carefully pouring the liquid into a measurement container to obtain the desired amount, then having the person drink. The chief disadvantages of this method are that an additional tool, the measurement container, must be provided and the fluid has to be manually poured into the containers increasing the chances of spillage.
A second method consists of controlling the outlet of a liquid container by a tap and measuring the dispensed amount of liquid by reading the liquid level on a scale on the liquid container. Since the liquid container has to be held exactly vertically in order to correctly read the level of the liquid, and since at least one hand is needed in order to control the tap, this method is mainly restricted to liquid containers installed at a fixed location and is not convenient for small transportable bottles in a assisted care setting. Moreover, there is no record of refills with this method, and therefore it is often difficult to accurately determine the total consumption of liquid dispensed. Additionally, at least a part of the container needs to be transparent in order to observe the level of liquid. One other prevalent problem associated with such methods is the eventual warming and stagnation of the fluid. This causes the liquid to be less than desirable for ingestion by a person.
Peristaltic pumps are preferred for certain liquid dispensing applications due to their ability to pump fluids without any contact between the pump's components and the fluid. Roller-type peristaltic pumps are frequently encountered in laboratory, instrumentation, and light commercial settings. In a typical roller-type peristaltic pump system, one or more lengths of flexible tubing are contacted by a series of rollers that are mounted on a rotor so as to be capable of moving in a circular path, i.e., a circumferential, circular arc, over the tubing. The flexible tube is compressed between rollers and a circular backstop or race. The race has a surface adjacent to, and concentric with, the path of the rollers. As the occluded portion of the tube is advanced, the fluid in front of it is forced to travel through the tube. The rotor may be rotated by a variable-speed motor or other suitable drive. Peristaltic pump systems are known to offer very limited tubing life.
It would be of great advantage to have a liquid container capable of repeatedly dispensing a controlled, defined volume of liquid without using an additional measurement container or a tap. Additionally, it would be very convenient if dispensing a defined amount of liquid were continuously adjustable, with only minimum manual control of the apparatus necessary to establish the desired volume of liquid. It would be further advantageous if the dispensing of liquid to a person in a medical setting could be repeated until the container is empty, without any need of additional operations to be carried out, and with the rate, volume, and time of dispensing recordable and selectively controllable. Also, recirculation of the liquid through appropriate filters and cooling systems so as to prevent the warming and stagnation of the fluid, would provide a distinct advantage over the prior art.